Integrated ECR-PECVD and magnetron sputtering system for rare-earth-doped Si-based materials

We report on a novel hybrid deposition technique to dope silicon-based materials with optically active elements in a plasma enhanced chemical vapor deposition (PECVD) process using a magnetron sputtering source. This approach is in contrast to traditional methods of rare-earth doping of PECVD films that utilise a metal organic precursor to introduce the rare earth species into the host matrix. We investigated the influence of the sputtering power applied to the rare earth metal target, in this case terbium, and the argon (Ar) partial pressure on the optical properties and composition of terbium-doped silicon oxide (SiOx:Tb3+) thin films. The film morphology was determined using high-resolution transmission electron microscopy, Rutherford backscattering spectrometry, and elastic recoil detection. We demonstrated that employing this novel technique provides a wider range of control of the doping level, yet delivers a similar rare earth (terbium) content to that which can be achieved using a traditional metal organic process. While the terbium concentration was strongly influenced by the sputtering power, it was only slightly affected by the Ar partial pressure. The refractive index was calculated from variable angle spectroscopic ellipsometry analysis and shows a direct relationship with the sputtering power whereas the film thickness shows an inverse relationship. The optically active Tb3+ ions were successfully excited within the silicon dioxide host matrix and the green Tb3+ emission was visible by the naked eye.